1. Field of the Invention
The present invention relates to an in-vivo information acquiring apparatus which acquires in-vivo information of an inside of a living body and transmits the in-vivo information to an outside of the living body.
2. Description of the Related Art
In recent years, a swallowable capsule endoscope is proposed in a field of endoscope. The capsule endoscope has an imaging function and a radio communication function. After being swallowed by a subject from the mouth for an observation (examination), the capsule endoscope travels through body cavities, for example, inside internal organs such as a stomach and a small intestine following peristaltic movements thereof until being naturally excreted. The capsule endoscope has a function of capturing an intra-subject image, for example, every 0.5 second during the travel.
While traveling through the body cavities, the capsule endoscope sequentially transmits image data acquired through image-pickup inside the body of the subject to the outside by radio communication. The transmitted image data is stored in a memory outside the body of the subject. The subject can move freely after swallowing the capsule endoscope until excreting the same by carrying a receiver which is equipped with a radio communication function and a memory function. After the subject excretes the capsule endoscope, a doctor or a nurse can make diagnosis looking at images of organs presented on a display based on the image data stored in the memory (see, for example, International Publication WO 01/35813).
Most of the capsule endoscopes are configured to obtain driving power from an embedded power source. A configuration proposed for the control of the driving of the capsule endoscope includes a reed switch which is provided inside the capsule endoscope and turned on and off in response to an external magnetic field, and a permanent magnet which is provided in a package housing the capsule endoscope to supply the magnetic field. The reed switch in such a capsule endoscope is configured to maintain an off-state while an external magnetic field of a predetermined level or a higher level of intensity is supplied, and to be turned on when the intensity of the external magnetic field lowers. Therefore, while housed inside the package, the capsule endoscope is not driven; and once taken out from the package and away from the influence of the permanent magnet, the capsule endoscope starts to be driven. When the capsule endoscope has such a configuration, the driving of the capsule endoscope can be prevented as far as the capsule endoscope is housed inside the package (see International Publication WO 01/35813).
Further, another proposed capsule endoscope is configured so that power supply from a power source to function execution units such as an imaging unit is turned on and off according to toggle operations controlled according to external control signals such as a magnetic field generated by a magnet. In this case, the power supply from the power source can be turned on and off at any time even when the capsule endoscope is in the package as far as the capsule endoscope has not been introduced inside the subject, whereby unnecessary power consumption of the power source and unnecessary radiation of electric waves can be prevented (see Japanese Patent Application Laid-Open No. 2005-81005).
However, when a magnet is made to continuously move at high speed around the above-mentioned conventional capsule endoscope, which is turned on and off according to toggle operations, the interval of toggle operations shortens.
Hence, it is necessary to prevent the shortening of the interval of toggle operations, e.g., by preventing the high-speed movements of the magnet around the capsule endoscope, particularly when the capsule endoscope includes circuitry in which resetting of an internal circuit is necessary after the power is once turned off and turned on again, so that the time necessary for the resetting is secured.
Further, since the capsule endoscope in general has a limitation in the amount of mountable power supply, power consumption of stand-by circuits must be minimized.